The specific objectives are to investigate sensitivity to altered glomerular basement membrane in progressive glomerulonephritis employing cellular immune assays. Specifically, we will use a preparation of altered glomerular basement membrane to which we have demonstrated patients with certain histologic forms of glomerulonephritis have cellular reactivity. We will attempt to purify and isolate this antigen for use in a radioimmunoassay and for antigen binding cells. We will investigate the effect of this antigen on non-specific lymphotoxin release by sensitized lymphocytes. We will also investigate target cell specific cytotoxicity in glomerulonephritis. Finally, we will correlate our findings with the presence of circulating immune complexes. In addition, reactivity to cross-reactive streptococcal cell membranes will be investigated.